A further study, looking more specifically at DSBs via neutral comet assays, demonstrated an increase in the damage for up to 48 h post irradiation, highlighting persistent unrepairable DSBs following pre-treatment with the Chk1 inhibitor AZD7762 in UMSCC-1 head and neck squamous cell carcinoma (HNSCC) cells [97]. The gene discussed is CHEK1; the disease is head and neck squamous cell carcinoma.